checker: correct type check for generic function with ternary if return (#9296)

vlib/v/checker/checker.v

@@ -5027,6 +5027,13 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) table.Type {
 					}
 					continue
 				}
+				if c.expected_type.has_flag(.generic) {
+					if node.typ == table.void_type {
+						node.is_expr = true
+						node.typ = c.unwrap_generic(c.expected_type)
+					}
+					continue
+				}
 				last_expr.typ = c.expr(last_expr.expr)
 				if !c.check_types(last_expr.typ, node.typ) {
 					if node.typ == table.void_type {

vlib/v/tests/if_expression_test.v

@@ -22,11 +22,7 @@ fn test_if_expression_with_stmts() {
 	}
 	assert a == 1
 	mut b := 0
-	b = if false {
+	b = if false { 42 } else { 24 }
-		42
-	} else {
-		24
-	}
 	assert b == 24
 }
 
@@ -164,18 +160,22 @@ fn test_if_expr_with_infix() {
 }
 
 fn test_multi_if_expr_with_infix() {
-	a := if 1 == 0 { 1 } else if 1 == 0 { 2 } else { 3 } + 4
+	a := if 1 == 0 {
+		1
+	} else if 1 == 0 {
+		2
+	} else {
+		3
+	} + 4
 	assert a == 7
 }
 
 fn test_if_expr_with_array_map() {
 	num_string := '2 3'
 
-	assigned := if num_string.len > 1 {
+	assigned := if num_string.len > 1 { num_string.split(' ').map(it.int()) } else { [
-		num_string.split(' ').map(it.int())
+			789,
-	} else {
+		] }
-		[789]
-	}
 
 	println(assigned)
 	assert assigned == [2, 3]
@@ -191,3 +191,11 @@ fn test_if_epxr_with_array_conditions() {
 		assert false
 	}
 }
+
+fn min<T>(a T, b T) T {
+	return if a < b { a } else { b }
+}
+
+fn test_if_expr_with_fn_generic() {
+	assert min(42, 13) == 13
+}